And today, another wave of scathing criticism of the state department and cia over the bloody attack on the u.S. Consulate in benghazi, the one that killed four americans. Abc's chief white house correspondent jonathan karl has what we learned today we did not know before. Reporter: It was a brazen attack that left a us consulate in flames and four americans dead, including us ambassador christopher stevens. The september 11, 2012, attacks in benghazi, libya, is both a tragedy and political football. But now, after an extensive year-long investigation the senate intelligence committee's conclusion, the attack was preventable. There were no protests prior to the attacks as the white house first claimed. At least 60 attackers penetrated the consulate while ambassador stevens was inside. Five extremist groups took part, all with ties to al qaeda. Most damning, the report concludes there was ample strategic warning that u.S. Facilities and personnel in benghazi were at risk. And that the state department failed to increase security. On one key point, the report backs uphite house. It says there were no u.S. Military resources nearby that could have help defend the compound. In fact, both the state department and ambassador stevens himself turned down an offer from the military to keep a special forces unit in libya a month before the attacks. Overall, the report is critical of the state department, which, of course, was headed at the time by hillary clinton. Her spokesperson referred questions today to the state department, which acknowledged the obvious security lapse that night in benghazi. But disputed the notion that the attacks could have been prevented, saying there was no specific threat against the consulate. Diane? Jonathan karl, reporting from

This transcript has been automatically generated and may not be 100% accurate.

Now Playing: Special counsel subpoenas the Trump Organization for Russia documents

Now Playing: NASA study reveals gene changes between twin astronauts

Now Playing: East Coast eyes possible 4th nor'easter for early next week

Now Playing: Founder of blood-testing company charged with massive fraud

Now Playing: {{itm.title}}

{"id":21549808,"title":"New Report on Benghazi Says Warnings Were Missed","duration":"3:00","description":"Bloody attack that killed four Americans might have been prevented.","url":"/WNT/video/report-benghazi-warnings-missed-21549808","section":"WNT","mediaType":"default"}